Optical beam steering and sampling apparatus and method

Abstract

In a light (optical) beam steering/sampling system, a matrix inversion control technique is used to decouple the operation of the actuators which drive the steering mirrors. The control technique uses two virtual variables, each having an associated independent feedback loop operating in a non-cross-coupled manner, each variable being associated with one of the two steering mirrors.

The invention claimed is: 
     
       1. Apparatus comprising:
 a first steering reflector on which a beam of light is incident; 
 a second steering reflector on which light reflected from the first steering reflector is incident; 
 a first beam splitter on which light reflected from the second steering reflector is incident; 
 a second beam splitter on which light reflected from the first beam splitter is incident; 
 a first detector on which light reflected from the first beam splitter is incident; and 
 a second detector on which light transmitted by the second beam splitter is incident; 
 wherein a first value is obtained which is a function of an output signal of both detectors is indicative of a state of the first steering reflector and not of the second steering reflector, and a second value is obtained which is a function of an output signal of both detectors is indicative of a state of the second steering reflector and not of the first steering reflector. 
 
     
     
       2. The apparatus of  claim 1 , further comprising a controller coupled between the detectors and the steering reflectors, whereby the controller changes the state of the first steering reflector responsive to the first value and not the second value and changes the state of the second steering reflector responsive to the second value and not the first value. 
     
     
       3. The apparatus of  claim 2 , the controller including two control loops, one control loop being associated with each of the first and second values. 
     
     
       4. The apparatus of  claim 2 , wherein the controller includes means for calibrating the apparatus. 
     
     
       5. The apparatus of  claim 1 , each steering reflector including a reflector coupled to an actuator. 
     
     
       6. The apparatus of  claim 5 , each steering reflector having a second actuator coupled to the reflector to tilt the reflector in a direction substantially orthogonal to a direction in which the first actuator tilts that reflector. 
     
     
       7. The apparatus of  claim 1 , wherein light transmitted by the first beam splitter is directed out of the apparatus. 
     
     
       8. The apparatus of  claim 1 , further comprising a third reflector positioned to reflect the light transmitted by the second beam splitter to the second detector. 
     
     
       9. The apparatus of  claim 1 , wherein each of the first and second values is obtained as a function of a displacement and an angle of the light beam incident on the apparatus. 
     
     
       10. The method of  claim 1 , further comparing a first lens located to focus light onto the first detector and a second lens located to focus light onto the second detector. 
     
     
       11. The apparatus of  claim 1 , wherein the first value and the second value respectively do not correspond to pointing or displacement of the beam of light. 
     
     
       12. Method for operating an optical apparatus having two steering reflectors, comprising the acts of:
 splitting light reflected serially from the two steering reflectors; 
 splitting the split light, into two portions; 
 detecting a first portion of the twice split light; 
 detecting a second portion of the twice split light; 
 obtaining a first value which is a function of an output signal from both acts of detecting, the first value being indicative of a state of the first steering reflector and not of the second steering reflector; and 
 obtaining a second value which is a function of an output signal from both acts of detecting, the second value being indicative of a state of the second steering reflector and not of the first steering reflector. 
 
     
     
       13. The method of  claim 12 , further comprising the act of:
 controlling a state of the first steering reflector responsive to the first value and not the second value, and controlling a state of the second steering reflector responsive to the second value and not the first value. 
 
     
     
       14. The method of  claim 13 , the controlling including:
 providing two control loops, one control loop being associated with each of the first and second values. 
 
     
     
       15. The method of  claim 12 , further comprising the act of changing the state of each steering reflector by an actuator. 
     
     
       16. The method of  claim 15 , further comprising the act of providing a second actuator associated with each steering reflector to tilt the steering reflector in a direction substantially orthogonal to a direction in which the first actuator tilts that reflector. 
     
     
       17. The method of  claim 12 , further comprising the act of directing externally a portion of the light which is split from the first act of splitting. 
     
     
       18. The method of  claim 12 , further comprising the act of reflecting the second portion of the twice split light prior to the act of detecting same. 
     
     
       19. The method of  claim 12 , wherein each of the first and second values is obtained as a function of a displacement and an angle of incident light. 
     
     
       20. The method of  claim 12 , further comprising the act of calibrating the optical apparatus. 
     
     
       21. The method of  claim 12 , further comprising the act of focusing the light prior to detecting same. 
     
     
       22. The method of  claim 12 , wherein the two values respectively do not correspond to pointing or displacement of the light.